This invention relates to a process for production of solid glucose from biomass materials, and more particularly, for means to separate the acid from the glucose and produce solid glucose for shipping to the end user (such as a gasohol plant) where glucose is fermented to form alcohol for blending with gasoline. The solid glucose can be fermented or purified and used as a food additive.
In the case of glucose fermentation, glucose can be produced from several carbohydrate containing materials such as starchy grains and cellulosic biomass materials. Starchy materials, such as corn, are converted by hydrolysis of starch to glucose by acids or enzymes. For enzyme hydrolysis, grain must be ground into mash to assure that the carbohydrates are accessible to enzymes. The mash must be sterilized before the enzymes are added and kept sterile in order for the enzymes to perform as required. The mash must be temperature and pH adjusted as required by the enzymes. Either acid or base may be required to adjust the pH. The first enzyme will convert the starch to water soluble dextrins. The second enzyme, after required temperature and pH adjustments, will hydrolyze the dextrins to glucose.
Dilute acid hydrolysis of starchy materials converts the starch to glucose. The resulting hydrolyzate must be neutralized with lime or other basic material before glucose can be used for fermentation. Biomass hydrolysis plants producing glucose, are usually operated at or near an ethanol fermenting and distilling process plant to avoid high costs of shipping dilute solutions of glucose.
Enormous amounts of cellulosic materials found in biomass are potentially convertible via hydrolysis to glucose. No practical cost-effective process for converting biomass materials to alcohol via fermentation and distillation has yet been developed. When such a process is available, a gasohol plant for starchy materials can be modified to require only a storage area for glucose. Thus, such a plant could process either starchy materials or glucose. The state of the art process usually adds dilute acid to a biomass in a reactor operating at high pressure and high temperature. Acids used for hydrolysis include sulfuric acid, hydrochloric acid, nitric acid, salts which can be hydrolyzed to form acids, and organic acids such as sulfonic acids. The hydrolyzate from the reactor contains dilute acid and dilute glucose. Large amounts of acid in the hydrolyzate, when neutralized with lime, results in high costs of acid and lime. Lime deposits form as scaling in evaporators and other equipment therefore lime may cause problems. Disposal problems often result in water pollution from neutralization. Separation of acid from the hydrolyzate by electrodialysis, ion exchange, solvent separation or other processes have the disadvantages of short equipment life, high capital costs, high operating costs, and high maintenance costs.
Also, a process for converting biomass to glucose uses low temperature and enzymes. The slow-acting process must use sterilized biomass in sterilized reactors. The costs of the enzymes is much more than that for acids.
Solid glucose manufactured for food requires pure glucose separated from impurities. Glucose from acid hydrolysis of corn starch produces a hydrolyzate that is then neutralized and purified by several steps including filtration, ion exchange, and absorption by activated charcoal to remove most of the impurities. The hydrolyzate is then concentrated via multiple-effect evaporation to remove most of the water. The resulting concentrated mixture is sent to a cooler and then to a crystallizer to form glucose crystals for separation from any remaining impurities. About 72 hours is required to form the glucose crystals. The resulting glucose crystals are separated from adhering liquor by a centrifuge. After water washing, the glucose is dried and stored for shipping.
It is therefore an object of this invention to obviate many of the limitations or disadvantages of the prior art in production of solid glucose by forming a glucose phase from a mixture of glucose and an acid.
Another object of this invention is to form a glucose phase in about 12 hours.
Still another object of this invention is to separate acid from glucose, so acid can be recovered for recycling. Recovered acid may contain glucose and can be recycled with the acid.
Additional purification of solid glucose may also be achieved to remove impurities to produce nearly pure glucose for food usage.
An additional object of this invention is to produce solid glucose from local sources of biomass for shipping to remote fermentation cites.
With the above and other objects in view, this invention relates to the novel features and alternatives and combinations presently described and pointed out in the drawings.